Methods for supporting substrates during fabrication of one or more objects thereon by programmable material consolidation techniques

ABSTRACT

A programmed material consolidation apparatus includes at least one fabrication site and a material consolidation system associated with the at least one fabrication site. The at least one fabrication site may be configured to receive one or more fabrication substrates, such as semiconductor substrates. A machine vision system with a translatable or locationally fixed camera may be associated with the at least one fabrication site and the material consolidation system. A cleaning component may also be associated with the at least one fabrication site. The cleaning component may share one or more elements with the at least one fabrication site, or may be separate therefrom. The programmed material consolidation apparatus may also include a substrate handling system, which places fabrication substrates at appropriate locations of the programmed material consolidation apparatus.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/425,567, filed Nov. 11, 2002, the disclosure of whichis hereby incorporated in its entirety by this reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to apparatus foreffecting programmed material consolidation techniques, such asstereolithography, and, more particularly, to apparatus that areconfigured to fabricate features on semiconductor devices and relatedcomponents. The present invention also relates to programmed materialconsolidation methods that include use of such apparatus.

[0004] 2. Background of Related Art

[0005] Over the past decade or so, a manufacturing technique which hasbecome known as “stereolithography” and which is also known as “layeredmanufacturing” has evolved to a degree where it is employed in manyindustries.

[0006] Basically, stereolithography, as conventionally practiced,involves utilizing a computer, typically under control ofthree-dimensional (3-D) computer-aided design (CAD) software, togenerate a 3-D mathematical simulation or model of an object to befabricated. The computer mathematically separates or “slices” thesimulation or model into a large number of relatively thin, parallel,usually vertically superimposed layers. Each layer has definedboundaries and other features that correspond to a substantially planarsection of the simulation or model and, thus, of the actual object to befabricated. A complete assembly or stack of all of the layers definesthe entire simulation or model. A simulation or model which has beenmanipulated in this manner is typically stored and, thus, embodied as aCAD computer file. The simulation or model is then employed to fabricatean actual, physical object by building the object, layer by superimposedlayer. Surface resolution of the fabricated object is, in part,dependent upon the thickness of the layers.

[0007] A wide variety of approaches to stereolithography by differentcompanies has resulted in techniques for fabricating objects fromvarious types of materials. Regardless of the material employed tofabricate an object, stereolithographic techniques usually involvedisposition of a layer of unconsolidated or unfixed materialcorresponding to each layer of the simulation or model. Next, thematerial of a layer is selectively consolidated or fixed to at least apartially consolidated, partially fixed, or semisolid state in thoseareas of a given layer that correspond to solid areas of thecorresponding section of the simulation or model. Also, while thematerial of a layer is being consolidated or fixed, that layer may bebonded to a lower layer of the object which is being fabricated.

[0008] The unconsolidated material employed to build an object may besupplied in particulate or liquid form. The material may itself beconsolidated or fixed. Alternatively, when the unconsolidated materialcomprises particles, a separate binder material mixed therein or coatingthe particles may facilitate bonding of the particles to one another, aswell as to the particles of a previously formed layer.

[0009] Surface resolution of the features of a fabricated objectdepends, at least in part, upon the material being used. For example,when particulate materials are employed, resolution of object surfacesis highly dependent upon particle size, whereas when a liquid isemployed, surface resolution is highly dependent upon the minimumsurface area of the liquid which can be consolidated or fixed and theminimum thickness of a material layer that can be generated. Of course,in either case, resolution and accuracy of the features of an objectbeing produced from the simulation or model are also dependent upon theability of the apparatus used to consolidate or fix the material toprecisely track the mathematical instructions indicating solid areas andboundaries for each layer of material.

[0010] Toward that end, and depending upon the type and form of materialto be fixed, stereolithographic fabrication processes have employedvarious fixation approaches. For example, particles have beenselectively consolidated by particle bombardment (e.g., with electronbeams), disposition of a binder or other fixative in a manner similar toink-jet printing techniques, and focused irradiation using heat orspecific wavelength ranges. In some instances, thin, preformed sheets ofmaterial may be superimposed to build an object, each sheet being fixedto a next-lower sheet and unwanted portions of each sheet removed, astack of such sheets defining the completed object.

[0011] Early on in its development, stereolithography was used torapidly fabricate prototypes of objects from CAD files. Prototypes ofobjects might be built to verify the accuracy of the CAD file definingthe object (e.g., an object or negative of a mold to be machined) and todetect any design deficiencies and possible fabrication problems beforea design was committed to large-scale production. Stereolithographictechniques have also been used in the fabrication of molds. Usingstereolithographic techniques, either male or female forms on which moldmaterial might be disposed could be rapidly generated.

[0012] In more recent years, stereolithography has been employed todevelop and refine object designs in relatively inexpensive materials.Stereolithography has also been used to fabricate small quantities ofobjects for which the cost of conventional fabrication techniques isprohibitive, such as in the case of plastic objects that haveconventionally been formed by injection molding techniques. It is alsoknown to employ stereolithography in the custom fabrication of productsgenerally built in small quantities or where a product design isrendered only once. Finally, it has been appreciated in some industriesthat stereolithography provides a capability to fabricate products, suchas those including closed interior chambers or convoluted passageways,which cannot be fabricated satisfactorily using conventionalmanufacturing techniques. It has also been recognized in some industriesthat a stereolithographic object or component may be formed or builtaround another, pre-existing object or component to create a largerproduct.

[0013] Conventionally, stereolithographic apparatus have been used tofabricate freestanding structures. Such structures have been formeddirectly on a platen or other support system of the stereolithographicfabrication apparatus, which is located within the fabrication tank ofthe stereolithographic apparatus. As the freestanding structures arefabricated directly on the support system, there is typically no need toprecisely and accurately position features of the stereolithographicallyfabricated structure. As such, conventional stereolithographic apparatuslack machine vision systems for ensuring that structures are fabricatedat certain locations.

[0014] Moreover, conventional stereolithographic apparatus lack supportsystems, handling systems, and cleaning equipment which are suitable foruse with relatively delicate structures, such as semiconductorsubstrates and semiconductor devices that have been fabricated thereon.

[0015] Accordingly, there is a need for stereolithography apparatuswhich are configured to form structures on fabrication substrates, suchas semiconductor substrates and semiconductor device components andwhich include systems for accurately positioning the fabricatedstructures, supporting and handling the fabrication substrates, andcleaning excess and residual material from the fabrication substrates.

SUMMARY OF THE INVENTION

[0016] The present invention includes stereolithography apparatus andother programmable material consolidation apparatus and systems that areconfigured to fabricate features on semiconductor devices or oncomponents that are configured for use with semiconductor devices. Inaddition, the present invention includes stereolithographic and otherprogrammed material consolidation methods (e.g., stereolithography,layered object manufacturing (LOM), selective laser sintering (SLS),photopolymer jetting, selective particle atomization and consolidation(laser engineered net shaping, or “LENS”), and other so-called “rapidprototyping” technologies) that include use of apparatus according tothe present invention. As used herein, the term “stereolithography” andvariations thereof, where applicable, are intended to denote all typesof programmed material consolidation techniques and is used synonymouslywith the phrase “programmed material consolidation” and variationsthereof.

[0017] A programmed material consolidation apparatus, or“stereolithography apparatus” for simplicity, according to the presentinvention includes a fabrication tank, which is also referred to hereinas a “fabrication chamber” or even more broadly as a “fabrication site.”The fabrication tank includes a platen or other support system suitablefor carrying substrates upon which structures are to bestereolithographically fabricated, which may also be termed “fabricationsubstrates.” By way of example only, the fabrication tank and thesupport therein may be sized and configured to receive one or moresemiconductor substrates, each of which carries a plurality ofsemiconductor devices. Alternatively, or in addition, the platen orother support system may be configured to support freestandingstructures as they are fabricated. In addition, the fabrication tank mayinclude a reservoir that is configured to hold a volume ofunconsolidated material, such as a liquid polymer.

[0018] A material consolidation system is associated with thefabrication tank in such a way as to direct consolidating energy (e.g.,in the form of radiation, such as a laser beam or less-focusedradiation) to a surface of the quantity of unconsolidated materialwithin the reservoir of the fabrication tank. When selectiveconsolidation is desired, a high level of precision may be achieved whenthe consolidating energy is focused and the surface of the quantity ofunconsolidated material and the focal point for the consolidating energysubstantially intersect one another.

[0019] Optionally, a stereolithography apparatus that incorporatesteachings of the present invention may include a machine vision system.The machine vision system includes an optical detection element, such asa camera, as well as a controller or processing element, such as acomputer processor or a collection of computer processors, associatedwith the optical detection element. The optical detection element may bepositioned in a fixed location relative to the fabrication tank orconfigured to move relative to the fabrication tank.

[0020] When included as part of a stereolithographic apparatus thatincorporates teachings of the present invention, the optical detectionelement of a machine vision system is useful for identifying thelocations of recognizable features, including, without limitation,features on a fabrication substrate and features, such as fiducialmarks, at a fabrication site. For example, the optical detection elementmay be configured and/or located to “see” relatively large structures,such as those that can be seen by the naked eye (i.e., macroscopicstructures), such as the locations of semiconductor devices upon afabrication substrate. Alternatively, or in addition, the opticaldetection element may be configured and/or located to “see” very small,even microscopic structures.

[0021] Another optional feature of a stereolithographic apparatus of thepresent invention is a cleaning component. A cleaning component may bepositioned and configured to remove excess liquid polymer from afabrication substrate while the fabrication substrate remains positionedupon a support system that is associated with the fabrication tank. Sucha cleaning component may comprise at least a part of the fabricationtank and, thus, operate prior to introduction of another fabricationsubstrate into the fabrication tank. Alternatively, excess liquidpolymer may be removed from a fabrication substrate during or followingremoval thereof from the fabrication tank.

[0022] Additionally, a stereolithographic apparatus that incorporatesteachings of the present invention may include a material reclamationsystem. The material reclamation system may be associated with one orboth of the fabrication tank and a cleaning component, if thestereolithographic apparatus includes a cleaning component. By way ofexample, the material reclamation system may collect material from thecleaning component and recycle the same into the fabrication tank.

[0023] A programmed material consolidation system that incorporatesteachings of the present invention may include a plurality offabrication sites and share a common material consolidation system,machine vision system, handling system, cleaning component, or materialreclamation system.

[0024] The present invention also includes methods for calibratingstereolithographic apparatus that incorporate teachings of the presentinvention. For example, the locations at which unconsolidated materialmay be selectively consolidated may be calibrated with a machine visionsystem. As another example, the magnification of a machine vision systemmay be calibrated. Also, a material consolidation system of astereolithographic apparatus according to the present invention may becalibrated to optimize the linearity with which selectivelyconsolidating energy impinges on a surface of unconsolidated material.

[0025] Programmed material consolidation fabrication processes,including methods of using each of the features described herein, arealso within the scope of the present invention. In particular,stereolithographic fabrication processes that incorporate teachings ofthe present invention include the use of stereolithographic techniquesto fabricate features on another structure, or fabrication substrate,such as a semiconductor substrate or semiconductor device component(e.g., a lead frame, a circuit board, etc.).

[0026] Other features and advantages of the present invention willbecome apparent to those of skill in the art through consideration ofthe ensuing description, the accompanying drawings, and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In the drawings, which depict exemplary embodiments of variousfeatures of the present invention:

[0028]FIG. 1 is a schematic representation of various possible elementsof a stereolithographic apparatus for fabricating features onsemiconductor devices or associated components in accordance with thepresent invention, the elements including a fabrication tank, a materialconsolidation system, a machine vision system, a cleaning component, anda material reclamation system;

[0029]FIG. 2 schematically depicts an exemplary stereolithographicapparatus in which a single material consolidation system and/or asingle machine vision system may be shared by a plurality of fabricationtanks;

[0030]FIG. 3 schematically depicts an exemplary embodiment offabrication tank that may be used in a stereolithographic apparatus ofthe present invention, the fabrication tank including a cavity and areservoir which are continuous with one another;

[0031]FIG. 3A illustrates an exemplary support element of thefabrication tank of FIG. 3, which support element has a substantiallyplanar support surface;

[0032]FIG. 3B shows another exemplary support element of the fabricationtank shown in FIG. 3, which support element includes recesses formed inthe support surface thereof;

[0033]FIG. 3C illustrates an exemplary volume control element of thefabrication tank depicted in FIG. 3, which volume control element isconfigured to add unconsolidated material to and/or removeunconsolidated material from the reservoir of the fabrication tank;

[0034]FIG. 3D depicts another exemplary volume control element of thefabrication tank of FIG. 3, which volume control element is configuredto displace unconsolidated material located within the reservoir of thefabrication tank;

[0035]FIG. 3E schematically depicts a stereolithographic fabricationtank which includes another variation of volume control and surfacelevel control element;

[0036]FIG. 4 schematically depicts another embodiment of fabricationtank that includes a rotatable support element and which may be used ina stereolithographic apparatus according to the present invention, suchas those shown in FIGS. 1 and 2, which fabrication tank also comprises acleaning component and a material reclamation system;

[0037]FIG. 4A is a top view of an example of a retention system for usewith a support system of the fabrication tank of FIG. 4;

[0038]FIG. 4B is a cross-section taken along line 4B-4B of FIG. 4A;

[0039]FIG. 4C is a top view of another example of a retention system foruse with a support system of the fabrication tank of FIG. 4;

[0040]FIG. 4D is a cross-section taken along line 4D-4D of FIG. 4C;

[0041]FIG. 4E is a cross-sectional representation of another embodimentof support system that may be used in a fabrication tank of asemiconductor fabrication apparatus according to the present invention;

[0042]FIG. 4F is a top view of the support system shown in FIG. 4E;

[0043]FIG. 5 is a schematic representation of still another exemplaryembodiment of fabrication tank that incorporates teachings of thepresent invention;

[0044]FIG. 6 is a schematic representation of an exemplary embodiment ofa material consolidation system according to the present invention,which is configured to focus consolidating energy so as to selectivelyconsolidate unconsolidated material which has been placed over afabrication substrate;

[0045]FIG. 7 schematically depicts another exemplary embodiment ofmaterial consolidation system, which is configured to generallyconsolidate unconsolidated material which has been placed over afabrication substrate;

[0046]FIG. 8 schematically illustrates an exemplary embodiment ofmachine vision system that may be used with a fabrication tank of astereolithographic apparatus according to the present invention, withthe machine vision system being configured to move relative to a surfaceof unconsolidated material which is to be consolidated by thestereolithographic apparatus;

[0047]FIG. 9 is a schematic representation of another exemplaryembodiment of machine vision system, which embodiment is configured toremain at a fixed location relative to a surface of unconsolidatedmaterial which is to be consolidated by a stereolithographic apparatuswith which the machine vision system is used;

[0048]FIG. 10 is a schematic representation of another embodiment ofcleaning component, as well as an exemplary embodiment of a materialreclamation system;

[0049]FIG. 11 is a schematic representation of yet another embodiment ofcleaning component that may be used as part of a stereolithographicapparatus according to the present invention;

[0050]FIG. 12 is a schematic representation of the manner in which thelocations at which a layer of unconsolidated material is selectivelyconsolidated may be calibrated with a machine vision system of astereolithographic apparatus of the present invention;

[0051]FIG. 13 is a top view of a fabrication tank, depicting anexemplary manner in which a linearity calibration may be conducted; and

[0052]FIG. 14 is a cross-sectional representation of a fabricationsubstrate and an object being stereolithographically fabricated thereonin accordance with teachings of the present invention.

DETAILED DESCRIPTION

[0053] An exemplary stereolithographic apparatus 10 for fabricatingfeatures on semiconductor substrates 52, semiconductor devices 54 orassociated components (e.g., lead frames, circuit boards, etc.) (notshown) or other fabrication substrates 50 is schematically depicted inFIG. 1. As shown, stereolithographic apparatus 10 includes a fabricationtank 100 and a material consolidation system 200, a machine visionsystem 300, a cleaning component 400, and a material reclamation system500 that are associated with fabrication tank 100. The depictedstereolithographic apparatus 10 also includes a substrate handlingsystem 600, such as a rotary feed system or linear feed system availablefrom Genmark Automation Inc. of Sunnyvale, Calif., for movingfabrication substrates 50 from one system of stereolithographicapparatus to another. Features of one or more of the foregoing systemsmay be associated with one or more controllers 700, or processingelements, such as computer processors or smaller groups of logiccircuits, in such a way as to effect their operation in a desiredmanner.

[0054] Controller 700 may comprise a computer or a computer processor,such as a so-called “microprocessor,” which may be programmed to effecta number of different functions. Alternatively, controller 700 may beprogrammed to effect a specific set of related functions or even asingle function. Each controller 700 of stereolithographic apparatus 10may be associated with a single system thereof or a plurality of systemsso as to orchestrate the operation of such systems relative to oneanother.

[0055] Fabrication tank 100 includes a chamber 110 which is configuredto contain a support system 130. In turn, support system 130 isconfigured to carry one or more fabrication substrates 50. By way ofexample only, the types of fabrication substrates 50 that support system130 may be configured to carry may include, without limitation, a bulksemiconductor substrate 52 (e.g., a full or partial wafer ofsemiconductive material, such as silicon, gallium arsenide, indiumphosphide, a silicon-on-insulator (SOI) type substrate, such assilicon-on-ceramic (SOC), silicon-on-glass (SOG), or silicon-on-sapphire(SOS), etc.) that includes a plurality of semiconductor devices 54thereon.

[0056] Fabrication tank 100 may also have a reservoir 120 associatedtherewith. Reservoir 120 may be continuous with chamber 110.Alternatively, reservoir 120 may be separate from, but communicate with,chamber 110 in such a way as to provide unconsolidated material 126thereto. Reservoir 120 is configured to at least partially contain avolume 124 of unconsolidated material 126, such as a photoimageablepolymer, or “photopolymer,” particles of thermoplastic polymer,resin-coated particles, or the like.

[0057] Photopolymers believed to be suitable for use with astereolithography apparatus 10 according to the present inventioninclude, without limitation, ACCURA® SI 40 HC and AR materials, ACCURA®SI 40 ND material, and CIBATOOL SL 5170, SL 5210, SL 5530, and SL 7510resins. The ACCURA® materials are available from 3D Systems, Inc., ofValencia, Calif., while the CIBATOOL resins are available from CibaSpecialty Chemicals Company of Basel, Switzerland.

[0058] Reservoir 120 or another component associated with one or both offabrication tank 100 and reservoir 120 thereof may be configured tomaintain a surface 128 of a portion of volume 124 located within chamber110 at a substantially constant elevation relative to chamber 110.

[0059] A material consolidation system 200 is associated withfabrication tank 100 in such a way as to direct consolidating energy 220into chamber 110 thereof, toward at least areas of surface 128 of volume124 of unconsolidated material 126 within reservoir 120 that are locatedover fabrication substrate 50. Consolidating energy 200 may comprise,for example, electromagnetic radiation of a selected wavelength or arange of wavelengths, an electron beam, or other suitable energy forconsolidating unconsolidated material 126. Material consolidation system200 includes a source 210 of consolidating energy 220. If consolidatingenergy 220 is focused, source 210 or a location control element 212associated therewith (e.g., a set of galvanometers, including one forx-axis movement and another for y-axis movement) may be configured todirect, or position, consolidating energy 220 toward a plurality ofdesired areas of surface 128. Alternatively, if consolidating energy 220remains relatively unfocused, it may be directed generally towardsurface 128 from a single, fixed location or from a plurality ofdifferent locations. In any event, operation of source 210, as well asmovement thereof, if any, may be effected under the direction ofcontroller 700.

[0060] When material consolidation system 200 directs focusedconsolidating energy 220 toward surface 128 of volume 124 ofunconsolidated material 126, stereolithographic apparatus 10 may alsoinclude a machine vision system 300. Machine vision system 300facilitates the direction of focused consolidating energy 220 towarddesired locations of features on fabrication substrate 50. As withmaterial consolidation system 200, operation of machine vision system300 may be proscribed by controller 700. If any portion of machinevision system 300, such as a camera 310 thereof, moves relative tochamber 110 of fabrication tank 100, that portion of machine visionsystem 300 may be positioned so as provide a clear path to all of thelocations of surface 128 that are located over each fabricationsubstrate 50 within chamber 110.

[0061] Optionally, as schematically depicted in FIG. 2, one or both ofmaterial consolidation system 200 (which may include a plurality ofmirrors 214) and machine vision system 300 of a stereolithographicapparatus 10 may be oriented and configured to operate in associationwith a plurality of fabrication tanks 100. Of course, one or morecontrollers 700 would be useful for orchestrating the operation ofmaterial consolidation system 200, machine vision system 300, andsubstrate handling system 600 relative to a plurality of fabricationtanks 100.

[0062] With returned reference to FIG. 1, cleaning component 400 ofstereolithographic apparatus 10 may also operate under the direction ofcontroller 700. Cleaning component 400 of stereolithographic apparatus10 may be continuous with a chamber 110 of fabrication tank 100 orpositioned adjacent to fabrication tank 100. If cleaning component 400is continuous with chamber 110, any unconsolidated material 126 thatremains on a fabrication substrate 50 may be removed therefrom prior tointroduction of another fabrication substrate 50 into chamber 110.

[0063] If cleaning component 400 is positioned adjacent to fabricationtank 100, residual unconsolidated material 126 may be removed from afabrication substrate 50 as fabrication substrate 50 is removed fromchamber 110. Alternatively, any unconsolidated material 126 remaining onfabrication substrate 50 may be removed therefrom after fabricationsubstrate 50 has been removed from chamber 110, in which case thecleaning process may occur as another fabrication substrate 50 ispositioned within chamber 110.

[0064] Material reclamation system 500 collects excess unconsolidatedmaterial 126 that has been removed from a fabrication substrate 50 bycleaning component 400, then returns the excess unconsolidated material126 to reservoir 120 associated with fabrication tank 100.

Fabrication Sites

[0065] Turning now to FIGS. 3-5, various exemplary embodiments offabrication sites, chambers, or tanks, that may be used in astereolithographic apparatus 10 (FIG. 1) or other programmable materialconsolidation apparatus or system that incorporates teachings of thepresent invention are illustrated.

[0066]FIG. 3 shows a fabrication tank 100′ which includes a chamber 110′that is continuous with a reservoir 120′. A support system 130′, whichincludes a platen, or support element 132′, a positioning element 140′,and an actuation element 146′, is located within reservoir 120′, beneathchamber 110′, and may be moved to a plurality of different verticalpositions, or elevations, therein.

[0067] A substrate-supporting surface of support element 132′, which isalso referred to herein as a support surface 134′ for the sake ofsimplicity, may be substantially planar, as shown in FIG. 3A.Alternatively, as depicted in FIG. 3B, support surface 134′ may have oneor more recesses 136′ formed therein, each recess 136′ being configuredto receive at least a portion of a fabrication substrate 50.Additionally, each recess 136′ may be configured to position afabrication substrate 50 in a desired orientation upon introduction ofthe same thereinto. Support surface 134′ may be configured to carry asingle fabrication substrate 50 or a plurality of fabrication substrates50.

[0068] Positioning element 140′ may be coupled to a bottom surface 138′of support element 132′ or otherwise operatively associated with supportelement 132′. Positioning element 140′ is depicted as being an elongatestructure that includes a coupling end 142′ that has been secured tobottom surface 138′, as well as an opposite, actuation end 144′.Nonetheless, positioning elements 140′ of other configurations are alsowithin the scope of the present invention. By way of example only,positioning element 140′ may comprise a hydraulically or pneumaticallyactuated piston, a screw, a linear actuator or stepper element, a seriesof gears, or the like.

[0069] Actuation element 146′ is, of course, associated with andconfigured to effect movement of positioning element 140′. Accordingly,examples of actuation elements 146′ that may be used as part of supportsystem 130′ include, but are not limited to, hydraulic actuators,pneumatic actuators, screw-drive motors, stepper motors, and other knownactuation means for controlling the movement of positioning element 140′in such a way as to cause support element 132′ to move from oneelevation to another in a substantially vertical direction and with ahigher degree of dimensional precision. Additionally, positioningelement 140′ and actuation element 146′ may desirably elevate supportelement 132′ and, thus, each fabrication substrate 50 thereon out ofchamber 110′ to facilitate movement of each fabrication substrate 50 bysubstrate handling system 600 (FIGS. 1 and 2). Alternatively, the levelat which surface 128 of volume 124 of unconsolidated material 126 islocated may be lowered below support surface 134′.

[0070] Control over the operation of actuation element 146′ and, thus,over the movement of positioning element 140′ and elevation of supportelement 132′ may be provided by controller 700 or another processingelement 105′ (e.g., a processor or smaller collection of logiccircuits), which may be dedicated for use with support system 130′ orfabrication tank 100′, in communication therewith, either as a part offabrication tank 100′ or, more generally, as a part ofstereolithographic apparatus.

[0071] Reservoir 120′ may include a surface level control element 150′which is configured to maintain surface 128 of volume 124 ofunconsolidated material 126 at a substantially constant elevation.Surface level control element 150′ may include a surface level sensor152′ and an element for adjusting volume 124 of unconsolidated material126, which element is referred to herein as a “volume adjustmentelement” 154′. Both surface level sensor 152′ and volume adjustmentelement 154′ may communicate with controller 700 or processing element105′, which monitors the level of surface 128, as indicated by signalsproduced and transmitted by surface level sensor 152′, and facilitatesadjustment or displacement of volume 124 by way of volume adjustmentelement 154′ to compensate for changes in the elevation of surface 128and thereby maintain surface 128 at a substantially constant elevation.

[0072] By way of example only, surface level sensor 152′ may comprise alaser sensor and reflected laser beam, which may be used in connectionwith one or more charge-coupled device (CCD) cameras or complementarymetal-oxide-semiconductor (CMOS) cameras. Triangulation techniques maybe used with such devices to determine the distance of surface 128 froma fixed point and, thus, the elevation, or level, at which surface 128is located.

[0073] If volume adjustment element 154′ is configured to change volume124 of unconsolidated material 126 within reservoir 120′, volumeadjustment element 154′ may comprise a pump 156′ or series of pumps 156′that may remove unconsolidated material 126 from reservoir 120′ andtransport the same to an external reservoir 158′, as well as addunconsolidated material 126 from an external reservoir 158′ to reservoir120′, as shown in FIG. 3C.

[0074] If volume adjustment element 154′ is instead configured todisplace a portion of volume 124 located within reservoir 120′, volumeadjustment element 154′ may, for example, comprise a piston or otherdisplacement member 160′ which may be incrementally introduced into andwithdrawn from reservoir 120′, as shown in FIG. 3D. Of course, movementof such a displacement member 160′ may be effected by an actuator 162′therefor, such as a hydraulic actuator, a pneumatic actuator, ascrew-drive motor, a stepper motor, or the like. Alternatively,vibrations may be transmitted directly to unconsolidated material 126by, for example, a piston face, diaphragm, or the like.

[0075] Alternatively, as shown in FIG. 3E, a volume adjustment element154″ may include one or more apertures or other openings 102 in a sidewall 101 of fabrication tank 100′ that have lower edges 103 that arepositioned at an elevation within fabrication tank 100′ at which surface128 of volume 124 of unconsolidated material 126 is to be maintained. Inaddition, surface level control element 154″ includes one or morereceptacles 104 that communicate with openings 102 to receiveoverflowing unconsolidated material 126 as support element 132′ an asubstrate or other workpiece thereon, as well as anystereolithographically fabricated objects, are lowered into fabricationtank 100′ and displace unconsolidated material 126 therein. A pumpingsystem or other material recycling element 105 may communicate with eachreceptacle 104 in such a way as to return overflowed unconsolidatedmaterial 126 to tank 100′ as support element 132′ is raised tofacilitate stereolithographic fabrication of one or more other objects.

[0076] The introduction of support element 132′ or one or morefabrication substrates 50 into a volume 124 of unconsolidated material126 contained within reservoir 120′ may result in the introduction ofgas or air bubbles into unconsolidated material 126. Accordingly,referring again to FIG. 3, fabrication tank 100′ may optionally includea bubble elimination system 165′ which is associated with a boundary orwall 114′ of reservoir 120′ or with support system 130′ so as tofacilitate the removal of air or gas bubbles (not shown) fromunconsolidated material 126. By way of example, bubble eliminationsystem 165′ may comprise an ultrasonic transducer of a known type (e.g.,a piezoelectric transducer), which causes fabrication tank 100′ orsupport system 130′ thereof to vibrate. Vibrations in fabrication tank100′ or support system 130′ are transmitted to unconsolidated material126 within reservoir 120′, causing any bubbles therein to dislodge froma structure to which they are adhered and float to surface 128, wherethey will pop or may be removed, such as by use of negative pressure.

[0077] Referring now to FIG. 4, another exemplary embodiment offabrication tank 100″ is illustrated. Fabrication tank 100″ includes areservoir 120″ at the base thereof and a chamber 110″ which is locatedover reservoir 120″ and which is continuous therewith. In addition,chamber 110″ of fabrication tank 100″ includes a material reclamationzone 170″, as well as a cleaning zone 180″ located above materialreclamation zone 170″.

[0078] As shown, reservoir 120″ may be configured to contain asubstantially constant volume 124 of material, including unconsolidatedmaterial 126 and, if stereolithographic processes have been initiated,consolidated material 126′ (FIG. 14). Accordingly, reservoir 120″ mayinclude a surface level control element 150′, such as that describedabove in reference to FIGS. 3, 3C, and 3D.

[0079] A support system 130″ of fabrication tank 100″ includes a supportelement 132″ which is positionable at a plurality of distinct, preciseelevations within reservoir 120″ and, optionally, within chamber 110″.Movement of support element 132″ is effected by a positioning element140″. Positioning element 140″ is, in turn, associated with an actuationelement 146″, which may be actuated to cause positioning element 140″ tomove so as to position support element 132″ at a desired elevationwithin reservoir 120″ or chamber 110″. Additionally, positioning element140″ may elevate support element 132″ and, thus, any fabricationsubstrates 50 thereon out of chamber 110″ to facilitate handling offabrication substrates 50 by substrate handling system 600 (FIGS. 1 and2). Actuation element 146″ may communicate with controller 700 orprocessing element 105′ in such a way that controller 700 directs theoperation of actuation element 146″.

[0080] In addition, actuation element 146″ may be configured to rotatesupport element 132″ about an axis A thereof and within a plane P inwhich support element 132″ is located. Alternatively, fabrication tank100″ may include a rotation element 148″ that is independent fromactuation element 146″ and which is configured to cause support element132″ to rotate. Such rotation may occur under instructions, in the formof signals or carrier waves, from controller 700 or processing element105′. By way of example and not by way of limitation, a stepper motor ora screw-drive motor that has been modified to move a screw, thenmaintain the screw in a substantially constant location when the screwhas reached one or more certain positions (e.g., material reclamationzone 170″ or cleaning zone 180″), may be used as either actuationelement 146″ or rotation element 148″.

[0081] When support element 132″ is moved into material reclamation zone170″ or cleaning zone 180″ of chamber 110″, actuation element 146″ orrotation element 148″ may cause support element 132″ to accelerate androtate at a sufficient speed that centrifugal force causes any excessunconsolidated material 126 and/or cleaning agents 127, such as water,solvents for unconsolidated material 126, detergents, combinationsthereof, or the like, to be removed from a fabrication substrate 50carried thereby while remaining substantially within the same plane asthat within which support element 132″ is located.

[0082] Material reclamation zone 170″ and cleaning zone 180″ may each beprovided with a receptacle 172″, 182″, respectively, that extendssubstantially around the periphery of an inner boundary or wall 114″ ofreservoir 120″. Receptacles 172″ and 182″ are each positioned atapproximately the same elevations within reservoir 120″ that supportelement 132″ will be located when positioned within reclamation zone170″ and cleaning zone 180″ thereof, respectively. Accordingly, asexcess unconsolidated material 126 and/or cleaning agents 127 areremoved, by spinning, from each fabrication substrate 50 that is carriedby support element 132″, receptacle 172″, 182″ will receivesubstantially all of the excess unconsolidated material 126 or cleaningagents 127 that are removed therefrom.

[0083] Since support element 132″ of fabrication tank 100″ is configuredto be rotated, or spun, at relatively high speed, support element 132″may be configured to retain one or more fabrication substrates 50 duringsuch rotation, or spinning. FIGS. 4A and 4B depict an example of aretention system 190 that may be used on a support element 132″ tosecure a fabrication substrate 50 in place thereon, particularly whensupport element 132″ is being accelerated to spin at high rotationalspeeds.

[0084] The depicted retention system 190 includes a raised periphery 191that forms a receptacle 192 within which a fabrication substrate 50 maybe substantially laterally contained. Thus, when support element 132″ isrotated, or spun, raised periphery 191 prevents a fabrication substrate50 that is being carried by support element 132″ from being thrownlaterally therefrom. One or more alignment features 193, which ensurethat fabrication substrate 50 has been properly positioned and orientedwithin receptacle 192, may also be formed by the inner border of raisedperiphery 191. In addition, retention system 190 may include one or moreaccess elements 194 which provide access to portions of an outerperiphery 55 of a fabrication substrate 50 located within receptacle192, thereby facilitating removal of fabrication substrate 50 fromreceptacle 192, as well as placement of another fabrication substrate 50therein.

[0085] Optionally, raised periphery 191 may protrude above an uppersurface 56 of fabrication substrate 50 a distance which comprises amaximum distance a stereolithographically fabricated object (not shown)may protrude from upper surface 56. Unconsolidated material 126 that isintroduced onto upper surface 56 of fabrication substrate 50 may belaterally contained by raised periphery 191. An upper surface 22U′ ofthe uppermost layer 22′ of unconsolidated material 126 within theconfines of raised periphery 191 may be planarized by translating aplanarizing element 195, such as a meniscus blade (which includes ameniscus at the trailing edge thereof) or air knife, thereacross toremove unconsolidated material 126 and/or smooth upper surface 22U′. Anuppermost surface of raised periphery 191 defines the level at whichplanarizing element 195 may be translated across unconsolidated material126.

[0086] Raised periphery 191 may be an integral part of a support surface134″ of support element 132″, with the majority of retention system 190being formed in support surface 134″. Alternatively, retention system190 may be formed separately from the manufacture of support element132″ and secured to support surface 134″ thereof. By way of exampleonly, stereolithographic processes may be employed to fabricateretention system 190 on support surface 134″, such as by usingstereolithographic apparatus 16.

[0087] Additionally, retention system 190 may include a sealing element198, which may be positioned on support surface 134″ so as to underlieat least a periphery of a fabrication substrate 50 positioned thereover.By way of example only, sealing element 198 may comprise a somewhatflattened ring which is configured to seal against an outer periphery 55of fabrication substrate 50, as well as regions of bottom surface 51 offabrication substrate 50 which are located adjacent to outer periphery55. Such a sealing element 198 may prevent unconsolidated material 126from contacting bottom surface 51 of fabrication substrate 50 andsupport surface 134″ of support element 132″. Exemplary materials fromwhich sealing element 198 may be fabricated include, without limitation,compressible, resilient materials, such as silicone, polyurethane,ethylene vinyl alcohol (EVA), or the like.

[0088] Also, in order to secure fabrication substrate 50 in placerelative to support surface 134″, retention system 190 may include oneor more pressure ports 196, which are configured to communicate with apressure source 197 (e.g., a vacuum or an air compressor). As supportelement 132″ is configured to be rotated, each pressure port 196 may befitted with a valve 199, which seals that pressure port 196 whenpressure source 197 is not in communication therewith. Of course, suchvalves 199 are not necessary when support element 132″ does not rotate,as in fabrication tank 100′. As a negative pressure is applied throughthe one or more pressure ports 196 to a bottom surface 51 of fabricationsubstrate 50, the negative pressure pulls fabrication substrate 50against sealing element 198, sealing bottom surface 51 against sealingelement 198. In addition to securing fabrication substrate 50 oversupport surface 134″ and possibly providing a cushion for fabricationsubstrate 50, as noted previously, sealing element 198 may preventunconsolidated material from contacting bottom surface 51 and supportsurface 134″. Operation of pressure source 197 and, if necessary,communication thereof with pressure ports 196 may be under control ofcontroller 700, processing element 105′, or another processing elementthat is dedicated for use with retention system 190.

[0089]FIGS. 4C and 4D illustrate a variation of retention system 190′,which is useful with support element 132″ of fabrication tank 100″.Retention system 190′ includes one or more ejection elements 196′.Ejection elements 196′ are useful for removing fabrication substrate 50from receptacle 192, as well as for breaking a seal caused by thepresence of a negative pressure beneath fabrication substrate 50, whichis applied against at least a portion of bottom surface 51 thereof.Operation of ejection elements 196′ may be controlled by way of acontroller 700 in communication therewith. By way of example only, eachejection element 196′ may comprise a mechanical piston that may berecessed within support surface 134″ to facilitate placement of afabrication substrate 50 thereon or raised by an actuation element 197′(e.g., a pneumatic, hydraulic, or mechanical actuation element) toprotrude from support surface 134″ and eject a fabrication substrate 50from recess 192 and raise fabrication substrate 50 to facilitatinggrasping thereof by substrate handling system 600. In this example, itis actuation element 197′ that communicates with controller 700,processing element 105′, or another processing element and that operatesin accordance with instructive signals, or carrier waves, fromcontroller 700, processing element 105′, or the other processingelement.

[0090] Alternatively, referring again to FIGS. 4A and 4B, each ejectionelement 196′ may comprise a pressure port 196, which, as describedpreviously herein, communicates with one or more pressure sources 197. Anegative air pressure may be applied through pressure port 196 to abottom surface 51 of a fabrication substrate 50 to secure the same tosupport surface 134″. Conversely, a positive air pressure may be forcedthrough port 196 against bottom surface 51 to eject a fabricationsubstrate 50 from support surface 134″. As shown, each pressure source197 may communicate with controller 700, processing element 105′, oranother processing element (FIG. 4), which directs operation of pressuresource 197 by known means. The use of ejection element 196′ to applypositive air pressure to bottom surface 51 of fabrication substrate 50may also be used to break a seal, if any, between bottom surface 51 anda feature, such as a sealing element 198, of support element 132″.

[0091] Optionally, pressure ports 196 may be configured and the outputof pressure source 197 modulated so as to create a circulating airflowbeneath bottom surface 51 as positive pressure is forced therethrough,causing fabrication substrate 50 to be lifted off of support surface134″ in such a way as to hover thereover in accordance with Bernoulli'sLaw. Such an ejection element 196′ is, therefore, useful forfacilitating the grasping of fabrication substrate 50 by a substratehandling system 600 (FIGS. 1 and 2) of stereolithography apparatus 10,10′, as well as to remove any unconsolidated material 126 from supportsurface 134″.

[0092] Another embodiment of support system 130′″ that may be used in afabrication tank 100, 100′, 100″ of a stereolithographic apparatus 10,10′ according to the present invention is shown in FIGS. 4E and 4F.Support system 130′″ includes a support element 132′″ and a locking ring191′″ that surrounds at least a portion of outer periphery 55 offabrication substrate 50 to secure the same to support element 132′″.Locking ring 191′″ forms a receptacle 192′″ within which fabricationsubstrate 50 is laterally contained. An upper surface 56 of fabricationsubstrate 50, however, remains substantially exposed.

[0093] Locking ring 191′″ includes an upper, laterally inwardlyextending lip 193′″ which is configured to contact an upper surface 56of fabrication substrate 50. As locking ring 191′″ also defines a fixeddistance between a support surface 134′″ and lip 193′″, which distancemay not be the same as the thickness of a fabrication substrate 50 to bepositioned therebetween, one or more spacers 194′″ may be fabricated(e.g., stereolithographically) or positioned on support surface 134′″ sothat support system 130′″ may be tailored to accommodate thinnerfabrication substrates 50. Spacers 194′″ are also useful for preventingbottom surface 51 of fabrication substrate 50 from adhering to supportsurface 134′″ of support element 132′″. Support elements 132′″ of thistype, including stereolithographically fabricated support elements132′″, may be reused.

[0094] A thickness of lip 193′″ may define a maximum distance astereolithographically fabricated object (not shown) may protrude fromupper surface 56 of fabrication substrate 50. The thickness of lip 193′″may be increased by positioning or forming (e.g.,stereolithographically) an extension ring 202′″ thereon. Unconsolidatedmaterial 126 that is introduced onto upper surface 56 of fabricationsubstrate 50 may be laterally contained by lip 193′″. By way of exampleonly, unconsolidated material 126 may be introduced within the confinesof lip 193′″ and any extension rings 202′″ thereon by lowering supportsystem 130′″ beneath surface 128 (FIG. 4) of volume 124 ofunconsolidated material 126 so as to permit unconsolidated material 126to flow therein, then raising support system 130′″ so that an upper edgeof lip 193′″ or an extension ring 202′″ thereon is substantiallycoplanar with surface 128.

[0095] An upper surface 22U′ of the uppermost layer 22′ ofunconsolidated material 126 within the confines of lip 193′″ and anyextension rings 202′″ thereon may be planarized by translating aplanarizing element 195, such as a meniscus blade or air knife,thereacross (FIG. 4B). An uppermost surface of lip 193′″ or an extensionring 202′″ thereon defines the level at which planarizing element 195may be translated across unconsolidated material 126.

[0096] Optionally, with returned reference to FIG. 4, fabrication tank100″ may include a bubble elimination system 165′, such as thatdescribed in reference to FIG. 3. Alternatively, stereolithographicfabrication tanks 100, such as those that have chambers 110 withrelatively small volumes (e.g., which are sufficient to contain only asingle semiconductor substrate 52), may include bubble eliminationsystems that create a negative pressure, or vacuum, within the chambersthereof. Such a bubble elimination system may, for example, include oneor more sealing elements, which substantially seal stereolithographicapparatus 10 (FIG. 1) chamber 110, as well as a negative pressure sourcethat communicates at least with chamber 110 so as to facilitate thecreation of a negative pressure therein.

[0097] Turning now to FIG. 5, still another embodiment of fabricationtank 100′″ that may be used in a stereolithographic apparatus 10, 10′(FIGS. 1 and 2) according to the present invention is shown. Fabricationtank 100′″ includes substantially all of the same elements as theembodiment of fabrication tank 100″ described in reference to FIG. 4,except for reservoir 120″. Instead of an integral reservoir, such asreservoir 120″, fabrication tank 100′″ includes a dispenser 120′″ forapplying unconsolidated material 126, which is drawn from an externalreservoir 159′″, to a fabrication substrate 50. By way of example only,dispenser 120′″ may comprise a laminar flow dispenser or a spray nozzleof a known type. A laminar flow dispenser is currently preferred for useas material dispenser 120′″, as laminar flow would result in thepresence of fewer air bubbles in unconsolidated material 126 than wouldbe present if unconsolidated material 126 were sprayed onto fabricationsubstrate 50 and, thus, eliminate the need for removing such bubbles.Additionally, when dispensed with a laminar flow dispenser,unconsolidated material 126 may be applied to upper surface 56 offabrication substrate 50 without covering any structures that protrudetherefrom (e.g., solder balls that protrude from a semiconductor device54), thereby eliminating the need to subsequently remove consolidatedmaterial or unconsolidated material 126 from such structures. Dispenser120′″ may apply a predetermined quantity, or metered amount, ofunconsolidated material 126 onto fabrication substrate 50 to form asingle layer 22 or multiple layers 22 a, 22 b, etc. of unconsolidatedmaterial 126 thereon, which are to be sequentially dispensed and,possibly, sequentially consolidated.

[0098] Of course, operation of dispenser 120′″ may be controlled bycontroller 700 or by a processing element 105′″ (e.g., a processorsmaller group of logic circuits) that is associated with fabricationtank 100′″.

Material Consolidation System

[0099] Various exemplary embodiments of material consolidation systems200 (FIGS. 1 and 2) that may be used in a stereolithographic apparatus10 according to the present invention are shown in FIGS. 6 and 7.

[0100] With reference to FIGS. 1 and 6, a stereolithographic apparatus10 that incorporates teachings of the present invention may include amaterial consolidation system 200′ which is configured to direct afocused beam of consolidating energy, such as a laser beam 220′, into achamber 110 of a fabrication tank 100 and onto selected locations of asurface 128 of a volume 124 of unconsolidated material 126 which isexposed to chamber 110.

[0101] When a laser beam 220′ is employed as the consolidating energy,material consolidation system 200′ includes a laser 210′ of a known typethat generates laser beam 220′. By way of example only, laser 210′ mayinclude a source 211′ which is configured to generate light in theultraviolet (UV) range of wavelengths of electromagnetic radiation.Laser 210′ may also include one or more lenses 216 to focus a laser beam220′ that has been emitted by source 211′ to a desired resolution. Alocation control element 212′, such as a scan controller (e.g., agalvanometer) of a known type, may be associated with source 211′ oflaser 210′ in such a way as to control the path of a laser beam 220′emitted from source 211′ and, thus, to effect movement of laser beam220′. The operation of location control element 212′ and, thus, themovement of a laser beam 220′, may be controlled by controller 700 or aprocessing element 205′ (e.g., a processor or smaller group of logiccircuits) which is dedicated for use with laser 210′, in accordance witha CAD program and an accompanying CAD file for the object to befabricated.

[0102] It is well known that the resolution of a laser beam 220′ that isto be moved may be substantially maintained by keeping the path of laserbeam 220′ as constant (in this case, vertical) as possible. This may bedone by increasing the path length of that laser beam 220′ (e.g., toabout twelve (12) feet). Nonetheless, it may not be practical for astereolithographic apparatus 10 (FIG. 1) that incorporates teachings ofthe present invention to include a laser 210′ with a source 211′ that ispositioned a sufficient distance from surface 128 of volume 124 ofunconsolidated material 126 that is to be selectively consolidated bylaser beam 220′. Accordingly, laser 210′ may also include a suitablemirror 214′ or series of mirrors 214′ that results in a nonlinear pathfor laser 210′ to provide a desired path length L for laser beam 220′ ina fixed amount of available space. As depicted, the area of mirror 214′may be large enough to substantially cover the entire cone of possibleangles at which laser beam 220′ may be directed by location controlelement 212′ and, thus, to reflect laser beam 220′ from every possibledirection onto a corresponding location of surface 128.

[0103] Optionally, or as an alternative to the use of a location controlelement 212′, the position and/or orientation of one or more of mirrors214′ may be moved, such as by an actuator 215′ therefor (e.g., a motor).The operation of actuator 215′ and, thus, the movement of a mirror 214′associated therewith, may be controlled by controller 700.

[0104] The size of the “spot” 222′ of a laser beam 220′ that impinges onsurface 128 of unconsolidated material 126 to consolidate (e.g., cure)the same may be on the order of about 0.001 inch to about 0.008 inchacross. It is currently preferred that, when laser beam 220′ is movedacross surface 128 (i.e., in the X-Y plane), the resolution of laserbeam 220′ be ±0.0003 inch over at least a 0.5 inch×0.25 inch field froma predetermined center point C on surface 128, thereby providing a highresolution scan across an area of at least 1.0 inch×0.5 inch. Of course,it is desirable to have substantially this high a resolution across theentirety of surface 128 to be scanned by laser beam 220′, such areabeing termed the “field of exposure.”

[0105]FIG. 7 depicts another exemplary embodiment of materialconsolidation system 200″, which is configured to direct unfocused, orblanket, consolidating energy 220″ in the form of electromagneticradiation (e.g., light or a light beam) into a chamber 110 of afabrication tank 100 and onto a surface 128 of a volume 124 ofunconsolidated material 126 which is exposed to chamber 110.

[0106] A source 210″ of consolidating energy 220″ may remain in a fixedposition as consolidating energy 220″ is introduced into chamber 110 orsource 210″ may be moved, such as by an actuation system 217″ therefor.By way of example only, such an actuation system 217″ may comprise anX-Y plotter of a known type, which may operate and, thus, move source210″ under the direction of signals, or carrier waves, that have beentransmitted by controller 700 or by a processing element 205″ (e.g., aprocessor or smaller group of logic circuits) that controls operation ofmachine consolidation system 200″. Operation of source 210″ may be undercontrol of controller or processing element 205″.

[0107] Of course, when unconsolidated material 126 is nonselectivelyconsolidated by consolidating energy 220″ from source 210″, a machinevision system 300 (FIGS. 1 and 2) is not employed at that time.

Machine Vision System

[0108] With returned reference to FIG. 1, a stereolithographic apparatus10 according to the present invention that employs a materialconsolidation system 200 (e.g., material consolidation system 200′ shownin FIG. 6) which selectively consolidates material 126 may also includea machine vision system 300. It is currently preferred that the field ofvision of machine vision system 300 be substantially coextensive withthe field of exposure of a laser beam 220′ (FIG. 6) or otherconsolidating energy 220 employed by a material consolidation system 200to be used in conjunction with machine vision system 300.

[0109] Examples of different types of machine vision systems 300 thatmay be used in accordance with teachings of the present invention areillustrated in FIGS. 8 and 9.

[0110] In FIG. 8, a scanning embodiment of machine vision system 300′,or one which is configured to move relative to a chamber 110 of afabrication tank 100 (FIGS. 1 and 2) with which it is used, is depicted.Machine vision system 300′ includes a camera 310′ which may be carriedand moved over a fabrication substrate 50 by a scan element 312′. Scanelement 312′ positions camera 310′ in close proximity to (e.g., inchesfrom) surface 128 (FIG. 1) of volume 124 of unconsolidated material 126(FIG. 1) so as to enable camera 310′ to view minute features on afabrication substrate 50 (e.g., bond pads, fuses, or other circuitelements of a semiconductor device) that is located at or near surface128. Upon viewing fabrication substrate 50, camera 310′ communicatesinformation about the precise locations of such features (e.g., with anaccuracy of up to about ±0.1 mil (i.e., 0.0001 inch)) to a computer 320′of machine vision system 300′.

[0111] Camera 310′ may comprise any one of a number of commerciallyavailable cameras, such as CCD cameras or CMOS cameras available from anumber of vendors. Of course, the image resolution of camera 310′ shouldbe sufficiently high as to enable camera 310′ to view the desiredfeatures of fabrication substrate 50 and, thus, to enable computer 320′to precisely determine the positions of such features. In order toprovide one or more reference points for the features that are viewed bycamera 310′, camera 310′ may also “view” one or more fiducial marks 112within a chamber 110 (FIG. 1) of a fabrication tank 100 (FIG. 1) withwhich machine vision system 300′ is used.

[0112] Suitable electronic componentry, as required for adapting orconverting the signals, or carrier waves, that are output by camera310′, may be incorporated in a board 322′ installed in a computer 320′.Such electronic componentry may include one or more processors 324′,other groups of logic circuits, or other processing or control elementsthat have been dedicated for use in conjunction with camera 310′. Atleast one processing element 324′, which may include a processor 324′,another, smaller group of logic circuits, or other control element thathas been dedicated for use in conjunction with camera 310′, isprogrammed, as known in the art, to process signals that representimages that have been “viewed” by camera 310′ and respond to suchsignals.

[0113] A self-contained machine vision system available from acommercial vendor of such equipment may be employed as machine visionsystem 300′. Examples of such machine vision systems and their variousfeatures are described, without limitation, in U.S. Pat. Nos. 4,526,646;4,543,659; 4,736,437; 4,899,921; 5,059,559; 5,113,565; 5,145,099;5,238,174; 5,463,227; 5,288,698; 5,471,310; 5,506,684; 5,516,023;5,516,026; and 5,644,245. The disclosure of each of the immediatelyforegoing patents is hereby incorporated herein in its entirety by thisreference. Such systems are available, for example, from CognexCorporation of Natick, Mass. As an example, and not to limit the scopeof the present invention, the apparatus of the Cognex BGA InspectionPackage™ or the SMD Placement Guidance Package™ may be adapted for usein a stereolithographic apparatus 10 (FIG. 1) that incorporatesteachings of the present invention, although it is currently believedthat the MVS-8000™ product family and the Checkpoint® product line, thelatter employed in combination with Cognex PatMax™ software, may beespecially suitable for use in the present invention.

[0114] A response by computer 320′ may be in the form of instructionsregarding the operation of a material consolidation system 200 (FIGS. 1and 2), such as the selectively consolidating material consolidationsystem 200′ shown in FIG. 6. These instructions may be embodied assignals, or carrier waves. By way of example only, such responsiveinstructions may be communicated to controller 700 of stereolithographicapparatus 10, 10′ (FIGS. 1 and 2, respectively) or directly to aprocessing element 205′ (FIG. 6), such as a processor or group ofprocessors, associated with a material consolidation system 200 (FIGS. 1and 2) (e.g., material consolidation system 200′ shown in FIG. 6) withwhich machine vision system 300′ is used. Controller 700 or controlelement 205′ may, in turn, cause material consolidation system 200′ tooperate in such a way as to effect the stereolithographic fabrication ofone or more objects on fabrication substrate 50 precisely at theintended locations thereof.

[0115] Due to the close proximity of camera 310′ to surface 128 (FIG.1), the field of vision of camera 310′ is relatively small. In order toenable camera 310′ to view a larger area of surface 128 than that whichis “covered” by or located within the field of vision camera 310′, ascan element 312′ of a known type is configured to traverse camera 310′over at least part of the area of surface 128. Scan element 312′ is alsouseful for moving camera 310′ out of the path of any selectivelyconsolidating energy being directed toward surface 128. By way ofexample only, scan element 312′ may comprise an X-Y plotter or scannerof a known type. Generally, an X-Y plotter or scanner includes an x-axiselement 313′ and a y-axis element 315′ that intersect one another. Asdepicted, camera 310′ is carried by both x-axis element 313′ and y-axiselement 315′ and, thus, is positioned at or near the location wherex-axis element 313′ and y-axis element 315′ intersect one another.

[0116] X-axis element 313′ and y-axis element 315′ are both configuredto move relative to and, thus, to position camera 310′ at a plurality oflocations over a fabrication substrate 50. Movement of x-axis element313′ is effected by an actuator 314′ (e.g., a stepper motor andactuation system, such as a gear or wheel that moves x-axis element 313′along a track) that has been operatively coupled thereto, with actuator314′ being configured to cause x-axis element 313′ to move laterally(i.e., perpendicular to the length thereof) along a y-axis. Y-axiselement 315′ is operatively coupled to an actuator 316′ therefor, whichis configured to cause y-axis element 315′ to move laterally along anx-axis. Actuators 314′ and 316′ may be configured to move theirrespective x-axis element 313′ and y-axis element 315′ in asubstantially continuous fashion or in an incremental fashion. Movementof actuators 314′ and 316′ may be controlled by a processing elementsuch as computer 320′ or a scanning controller 326′, such as a processoror smaller group of logic circuits, that is dedicated to operation ofscan element 312′ and which may communicate with computer 320′ in such away as to provide computer 320′ with information as to the specificlocation of camera 310′ relative to surface 128 (FIG. 1).

[0117]FIG. 9 shows an embodiment of machine vision system 300″ thatincludes a camera 310″ which is mounted or otherwise secured in a fixedposition relative to surface 128 and may be maintained in a fixedposition relative to a chamber 110 of a fabrication tank 100 (FIGS. 1and 2) with which machine vision system 300″ is to be used. By way ofexample only, camera 310″ may be positioned in close proximity to amirror 214′ of material consolidation system 200′ (FIG. 6) or at anyother location which will provide camera 310″ with a substantiallyunobstructed field of vision that covers the areas within whichfabrication substrates 50 may be located.

[0118] Like camera 310′, which is described in reference to FIG. 8,camera 310″ may comprise a CCD camera, a CMOS camera, or any othersuitable type of camera. As camera 310″ is positioned farther away froma fabrication substrate 50 to be viewed thereby, however, camera 310″may have an effectively larger field of vision than camera 310′. Ofcourse, suitable optical and/or digital magnification technology may beassociated with camera 310″ to provide the desired level of resolution.Further, although camera 310″ may be locationally stationary, a suitablegimbals structure with rotational actuators may be employed to pointcamera 310″ at a specific location in the field of exposure with littleactual rotational movement. Thus, camera 310″ may be used for bothbroad, or “macro,” vision and viewing and inspection of miniaturefeatures.

[0119] While machine vision system 300″ lacks a scan element, theremaining features thereof may be the same as and operate in the same ora similar manner to the corresponding features of machine vision system300′, which is described in reference to FIG. 8.

[0120] Cleaning Component

[0121] Exemplary embodiments of cleaning components 400 that may be usedwith a stereolithographic apparatus 10 that incorporates teachings ofthe present invention, shown in FIG. 1, are depicted in FIGS. 4, 10, and11.

[0122] The embodiment of cleaning component 400′ shown in FIG. 4 isconfigured to be used with a fabrication tank 100″ that is configuredlike the one shown in FIG. 4. Cleaning component 400′ may include aninitial material removal component 410′ which is configured to removeexcess unconsolidated material 126 from a fabrication substrate 50, anapplicator 420′ which is configured to introduce one or more cleaningagents 127 (e.g., water, solvents, detergents, etc.) onto at least anexposed surface of fabrication substrate 50, and a secondary materialremoval component 430′ that removes cleaning agents 127 and any residualunconsolidated material 126 from fabrication substrate 50.

[0123] Initial material removal component 410′ of cleaning component400′ comprises support system 130″ of fabrication tank 100″, as well asmaterial reclamation zone 170″ of chamber 110″ and receptacle 172″ offabrication tank 100″. Support system 130″ and, in particular, actuationelement 146″ or rotation element 148″ thereof, is configured toaccelerate rotation of a fabrication substrate 50 carried thereby to arelatively high speed (e.g., about 50 to about 6,000 rpm) in such a waythat any unconsolidated material 126 thereon will be forced therefromunder centrifugal force along substantially the same plane as thatwithin which fabrication substrate 50 is located, into receptacle 172″,and prevented from falling into reservoir 120″.

[0124] Optionally, a protective cover 175 may be positioned beneathsupport element 132″ and over surface 128 of volume 124 ofunconsolidated material 126. Of course, protective cover 175 isconfigured to be placed in the appropriate location in such a way as toavoid contact with positioning element 140″. Accordingly, protectivecover 175 may include two or more sections 175 a, 175 b, one or more ofwhich is configured to accommodate positioning element 140″ upon beingmoved into position. Each section 175 a, 175 b of protective cover 175may, for example, be moved into position in a hinged fashion (i.e.,about hinges 177), as depicted, or by horizontally sliding each section175 a, 175 b into position. In order to move protective cover 175 intoposition, it may be operably coupled with an actuator 176 (e.g., amotor). Operation of actuator 176 and, thus, movement of protectivecover 175 may be directed by controller 700 or by a processing element178, such as a processor or smaller group of logic circuits, that isdedicated for use with cleaning component 400′.

[0125] As an alternative to forcing excess unconsolidated material 126which is removed from fabrication substrate 50 into receptacle 172″ byrotating, or spinning, unconsolidated material 126 may be caused to fallinto reservoir 120″ and, thus, captured directly thereby.

[0126] Once excess unconsolidated material 126 has been substantiallyremoved from fabrication substrate 50, positioning element 140″ is movedto raise support element 132″ from material reclamation zone 170″ tocleaning zone 180″.

[0127] By way of example only, applicator 420′ may comprise a fixed ormovable high-pressure spray nozzle or group of nozzles that form a sprayhead 421′, which is in flow communication with a source 422′ of cleaningagent 127 (e.g., water, solvents for unconsolidated material 126,detergents, etc.). Applicator 420′ is configured to be oriented so as todirect one or more cleaning agents 127 into chamber 110″ of fabricationtank 100″ and onto an exposed surface of a fabrication substrate 50 thatis carried by support system 130″ and located within cleaning zone 180″of chamber 110″.

[0128] Applicator 420′ may be located in a fixed position relative tofabrication tank 100″ or carried by a movable element 424′, such as arobotic arm, which is configured to position applicator 420′ so as toorient the same toward fabrication substrate 50, as depicted in FIG. 4.

[0129] Controller 700 or one or more dedicated processing elements 426′(e.g., a processor, a smaller group of logic circuits, etc.) thatcommunicate with controller 700, may communicate with applicator 420′and its associated movable element 424′, if any. Accordingly, operationof applicator 420′, including, without limitation, the orientation ofspray head 421′ and the application of cleaning agent 127 onto a surfaceof fabrication substrate 50, may be performed under the direction ofeither controller 700 or a dedicated processing element 426′.

[0130] Like initial material removal component 410′, secondary materialremoval component 430′ of cleaning component 400′ includes supportsystem 130″ of fabrication tank 100″. In addition, secondary materialremoval component 430′ includes cleaning zone 180″ and receptacle 182thereof of chamber 110″. Support system 130″ and, in particular,actuation element 146″ or rotation element 148″ thereof, is configuredto accelerate rotation of a fabrication substrate 50 carried thereby toa sufficiently high speed (e.g., about 50 to about 6,000 rpm) so thatany cleaning agents 127 or unconsolidated material 126 thereon will beforced therefrom along substantially the same plane as that within whichfabrication substrate 50 is located, into receptacle 172″, and preventedfrom falling into reservoir 120″.

[0131] Optionally, positive air pressure, which may be supplied by useof a so-called “air knife,” such as that depicted and described inreference to FIG. 11, may be positioned over each fabrication substrate50 following the cleaning process to dry any residual cleaning agents127 therefrom.

[0132] A variation of cleaning component 400′ does not comprise part ofa fabrication tank 100″ but, rather, is separate therefrom so as tocompletely avoid the potential for contamination of unconsolidatedmaterial 126 within reservoir 120″ with excess unconsolidated material126 being removed from fabrication substrate 50 with cleaning agents127.

[0133] Turning now to FIG. 10, another exemplary embodiment of cleaningcomponent 400″ is depicted. Cleaning component 400″ includes a materialremoval component 410″ and a wash element 420″, as well as a supportelement 430″ upon which one or more fabrication substrates 50 aresupported while material removal component 410″ and wash element 420″perform their intended tasks.

[0134] Material removal component 410″, which is positioned external tofabrication tank 100″, may comprise one or more removal heads 412″,through which either a negative pressure (e.g., a vacuum) or a positivepressure (e.g., about 30 psi (which is typically not sufficient topuncture the skin of an operator of stereolithographic apparatus 10,10′) or higher pressures may be used and delivered by a so-called “airknife”, such as that manufactured by Secomak Ltd. of Middlesex, UnitedKingdom, at a sufficient velocity to overcome the adhesion ofunconsolidated material 126 from fabrication substrate 50 and, thus,remove unconsolidated material 126 from fabrication substrate 50) may beapplied to a fabrication substrate 50. Each removal head 412″ may besupported by a positioning element 414″, such as a robotic arm.Positioning element 414″ places removal head 412″ in sufficientproximity to one or more surfaces of a fabrication substrate 50 so thata negative pressure (e.g., a vacuum) or positive pressure applied tofabrication substrate 50 by removal head 412″ may respectively draw anyexcess unconsolidated material 126 on fabrication substrate 50 intoremoval head 412″ or blow any excess unconsolidated material 126 fromfabrication substrate 50. Alternatively, support element 430″ may betransported so as to move fabrication substrate 50 in proximity to oneor more removal heads 412″. Material removal component 410″ may be usedin combination with a bulk removal process, such as tipping or invertinga fabrication substrate 50 to permit unconsolidated material 126 to flowtherefrom.

[0135] As fabrication substrate 50 is brought in proximity to washelement 420″ or wash element 420″ is brought into proximity tofabrication substrate 50, support element 430″ may remain secured tofabrication substrate 50. As shown, wash element 420″ may include one ormore spray heads 421″ that communicate with a source 422″ of cleaningagent 127 and which may be oriented to direct cleaning agent 127 ontofabrication substrate 50.

[0136] Any cleaning agent 127 that remains on fabrication substrate 50may be removed therefrom by way of one or more removal heads 412″, whichmay include at least one removal head 412″ that was used to removeexcess unconsolidated material 126 from fabrication substrate 50 or adifferent removal head 412″.

[0137] Another embodiment of cleaning component 400′″ that may be usedin a stereolithography apparatus 10, 10′ (FIGS. 1 and 2, respectively)according to the present invention is shown in FIG. 11. Cleaningcomponent 400′″ includes a tank 440′″ which is at least partially filledwith one or more cleaning agents 127 and within which one or morefabrication substrates 50 may be introduced, such as by the illustratedwafer boat 450′″. Additionally, cleaning component 400′″ may include anagitation system 460′″, which facilitates the removal of residualunconsolidated material from fabrication substrates 50. By way ofexample only, agitation system 460′″ may include a vertical agitationsystem, which repeatedly moves a support 452′″ upon which wafer boat450′″ is carried up and down.

[0138] As another alternative, a rotary wash system (not shown), such asthat available from Semitool of Kalispel, Mont., may be used to removeany residual unconsolidated material from one or more fabricationsubstrates.

Material Reclamation System

[0139] Again referring to FIGS. 4 and 10, an exemplary embodiment ofmaterial reclamation system 500, shown in FIG. 1, is illustrated.

[0140] As depicted in FIG. 4, material reclamation system 500 includes acollection conduit 510 which includes a first end 512 that communicateswith receptacle 172″ of cleaning component 400′ so as to receive excessunconsolidated material 126 which has been collected by receptacle 172″.When used with the embodiment of cleaning component 400″ that is shownin FIG. 10, first end 512 of collection conduit 510 communicates withmaterial removal component 410″, such as a negative pressure head, so asto collect excess unconsolidated material 126 that has been drawn intomaterial removal component 410″.

[0141] The opposite, second end 514 of collection conduit 510communicates with either reservoir 120′, 120″, as shown, or an externalreservoir 158′ (FIG. 3C) in communication therewith. Accordingly,unconsolidated material 126 may be returned to reservoir 120′, 120″, or158′ through collection conduit 510.

[0142] One or more filters 530, which are configured to permit thepassage of unconsolidated material 126 therethrough while trappingparticulate contaminants that are larger than a selected size, may alsobe positioned along the length of collection conduit 510 or at an end512, 514 thereof.

[0143] One or more pumps 520 (e.g., peristaltic pumps) may communicatewith collection conduit 510, each applying either a positive or negativepressure thereto, to facilitate the transport of unconsolidated material126 therethrough, as well as the return of unconsolidated material 126to reservoir 120′, 120″, 158′ through conduit 510.

Calibration of the Programmed Material Consolidation Apparatus

[0144] With returned reference to FIGS. 1, 2, and 6, as well as withreference to FIG. 12, machine vision system 300 (e.g., either a movablemachine vision system 300′, such as that shown in FIG. 8, or astationary machine vision system 300″, such as that shown in FIG. 9) maybe used to calibrate stereolithographic apparatus 10, 10′ and, moreparticularly, material consolidation system 200 (e.g., the selectivematerial consolidation system 200′ shown in FIG. 6) thereof. Varioustypes of calibration may be effected, including, but not limited to,calibration of the position (X-Y) at which a selectively consolidatingenergy, such as laser beam 220′, impinges upon surface 128 of volume 124of unconsolidated material 126, calibration of the magnification ofmachine vision system 300 and required movement of the selectivelyconsolidating energy to effect fabrication of a structure of desireddimensions, and calibration of the “squareness” of a grid of locationsat which the selectively consolidating energy impinges upon surface 128.

[0145] The position at which selectively consolidating energy impingesupon surface 128 may, by way example only, be calibrated by selectivelyconsolidating unconsolidated material 126 at one or more calibrationlocations, each of which is referred to herein as a “reference pixel”750, on surface 128. Next, each reference pixel 750 is “viewed” bymachine vision system 300 to locate the same relative to a referencegrid (not shown), which may be stored in memory of either computer 320′(FIG. 8) or controller 700 (FIG. 1). The location at which eachreference pixel 750 actually appears is then compared with theanticipated location 750′ for reference pixel 750. Materialconsolidation system 200, the reference grid, or a combination of bothmay then be adjusted, as known in the art, to compensate for anydifference between anticipated location 750′ and the actual location ofreference pixel 750.

[0146] The magnification with which a movable machine vision system300′, such as that shown in FIG. 8, views objects that are locatedwithin or exposed to chamber 110 may be determined by moving camera 310′a fixed distance and determining the number of reference pixels 750 thatare “viewed” (e.g., as changes in contrast sensed by camera 310′) ascamera 310′ is moved. For example, if camera 310′ is moved a lineardistance of 10 mils (i.e., 0.010 inch) and twenty (20) pixel widths(e.g., ten (10) pixels, each positioned one pixel width apart from eachother) are detected (e.g., as nineteen (19) changes, or transitions, incontrast), camera 310′ is magnifying a viewed image by a value whichequates to a 20:1 pixels-per-mil ratio. This process may then berepeated at least once to check the measured magnification of camera310′. Knowledge of the pixel-to-mil ratio is useful for controlling themovement of selectively consolidating energy, such as by controllingoperation of a location control element 212′ (e.g., pulsing of a steppermotor that moves a galvanometer) that moves a laser beam 220′ (FIG. 6).

[0147] A calibration plate (not shown) of a known type, which, ofcourse, is configured specifically for the type of apparatus to becalibrated, may be used to determine the magnification with which afixed camera 310″ of machine vision system 300″, shown in FIG. 9, viewsobjects that are located within or exposed to chamber 110. Thecalibration plate, which is also referred to as a “prime standard,”includes features of known dimensions and locations. These knowndimensions may be compared, as known in the art, with the image viewedby camera 310″ to determine the degree to which an image of thesefeatures is magnified or demagnified by camera 310″.

[0148] The linearity with which selectively consolidating energyimpinges upon surface 128 across the field of exposure of materialconsolidation system 200′ may be determined and calibrated bydetermining the actual locations 760 (FIG. 13), particularly at thecorners and edges of a rectangular field of exposure, at whichselectively consolidating energy, such as laser beam 220′, impinges onsurface 128. The actual locations 760 at which the selectivelyconsolidating energy impinges on surface 128 may then be compared tolocations 760′ (FIG. 13) that are anticipated if the selectivelyconsolidating energy were impinging on surface 128 in a linear path.Responsive to this comparison, movement of the selectively consolidatingenergy may be adjusted, or calibrated, in such a way as to increase thelinearity of the path along which the selectively consolidating energyimpinges on surface 128 and, thus, the accuracy with which theselectively consolidating energy impinges on surface 128, particularlyat the corners and edges of the field of exposure. In the example of alaser beam 220′, adjustments in the movement thereof may be effected byadjustments in the manner in which location control element 212′ (FIG.6), such as a pair of galvanometers, are moved.

[0149] With reference to FIG. 13, such linearity calibration may beeffected by positioning light-sensitive elements 770, such asphototransistors, CCD arrays, or CMOS arrays, at selected locationswithin chamber 110, such as at the four corners 116 thereof and alongthe edges 118 thereof, midway between two corners 116. Alternatively, alight-sensitive plate (not shown) of a known type (e.g., a largephototransistor, CCD array, or CMOS array) may be positioned withinchamber 110 at an elevation which is substantially the same as that atwhich surface 128 (FIG. 6) is to be maintained during stereolithographicfabrication. As another alternative, reference pixels 750 may be formedby use of material consolidation system 200′ (FIG. 6) and viewed bymachine vision system 300, 300′, 300″ (FIGS. 1, 2, 8, and 9).

Use of the Programmed Material Consolidation Apparatus

[0150] In reference again to FIGS. 1 and 2, as well as to FIG. 14, anexample of the use of a programmed material consolidation apparatus,such as stereolithographic apparatus 10, 10′, that incorporatesteachings of the present invention is described.

[0151] In order to stereolithographically fabricate one or more objects20, corresponding data from the stl files, which comprise a 3-D CADsimulation or model, resident in memory (e.g., random-access memory(RAM)) associated with controller 700 are processed by controller 700.The data, which mathematically represents the one or more objects to befabricated, may be divided into subsets, each subset representing alayer 22, or “slice,” of the object 20. The division of data may beeffected by mathematically sectioning the 3-D CAD model into at leastone layer 22, a single layer or a “stack” of such layers 22 representingthe object 20. Each slice may be from about 0.0001 inch to about 0.0180inch thick. A thinner slice promotes higher resolution by enablingbetter reproduction of fine vertical surface features of the object orobjects to be fabricated.

[0152] Before fabrication of a first layer 22 a of an object 20 iscommenced, the operational parameters for apparatus 10, 10′ may be setto adjust the size (diameter if circular) of selectively consolidatingenergy (e.g., laser beam 220′ shown in FIG. 6), if such is used to atleast partially consolidate unconsolidated material 126.

[0153] In addition, controller 700 may automatically check and, ifnecessary, adjust by means known in the art the elevation, or level, ofsurface 128 of volume 124 of unconsolidated material 126 to maintain thesame at an appropriate focal length for laser beam 220′. U.S. Pat. No.5,174,931, the disclosure of which is hereby incorporated herein in itsentirety by this reference, discloses an example of a suitable levelcontrol system. Alternatively, the height of a mirror 214′ (FIG. 6) thatreflects laser beam 220′ onto an appropriate location of surface 128 maybe adjusted responsive to a detected elevation of surface 128 to causethe focal point of laser beam 220′ to be located precisely at surface128, although this approach is more complex.

[0154] A support system 130, 130′, 130″, 130′″ upon which one or morefabrication substrates 50 (e.g., semiconductor substrates 52) arecarried may then be submerged in unconsolidated material 126 withinreservoir 120, 120′, 120″ to a depth equal to the thickness of one layer22 or slice of the object 20 to be formed so as to form a layer 22′ ofunconsolidated material 126 on fabrication substrate 50. The elevationof surface 128 may subsequently be readjusted, as required toaccommodate any differences between unconsolidated material 126 andconsolidated material 126′. Alternatively, a layer 22′ of unconsolidatedmaterial 126 may be disposed onto an exposed upper surface 56 offabrication substrate 50.

[0155] A machine vision system 300, 300′, 300″ (FIGS. 1 and 2, 8, and 9,respectively) may then be used to view fabrication substrate 50 and toidentify each location thereof over which an object 20 is to befabricated.

[0156] Laser 210′ (FIG. 6) may then be activated so laser beam 220′ willscan surface 128 of volume 124 of unconsolidated material 126 so as toat least partially consolidate (e.g., polymerize to an at leastsemisolid state) the same, thereby defining boundaries of a layer 22 ofobject 20 and filling in solid portions thereof. Support system 130,130′, 130″ may then be lowered to lower fabrication substrate 50 adistance that is substantially equal to the desired thickness of thenext layer 22 of object 20 to be fabricated thereover, and the selectiveconsolidation process repeated, as often as necessary, layer by layer,until each object 20 is completed. Of course, the number of layers 22that are required to form object 20 may depend upon the height of object20 and the desired thickness for each layer 22 thereof. Different layers22 of a stereolithographically fabricated object 20 may have differentthicknesses.

[0157] If desired, an uppermost layer 22U′ of unconsolidated material126 may be planarized, for example, by use of a planarizing element 195,such as that described in reference to FIG. 4B. Planarizing elements 195are particularly useful when one or more layers 22′ of unconsolidatedmaterial 126 are dispensed over fabrication substrate 50 rather thanbeing formed thereover by submersion.

[0158] With continued reference to FIG. 14, as well as to FIG. 7,unconsolidated material 126 of layer 22′ may be consolidated with lessselectivity by exposing layer 22′ to laser beam 220′ which has beenemitted from laser 210′ (not shown).

[0159] Although the foregoing description contains many specifics, theseshould not be construed as limiting the scope of the present invention,but merely as providing illustrations of some of the presently preferredembodiments. Similarly, other embodiments of the invention may bedevised which do not depart from the spirit or scope of the presentinvention. Moreover, features from different embodiments of theinvention may be employed in combination. The scope of the invention is,therefore, indicated and limited only by the appended claims and theirlegal equivalents, rather than by the foregoing description. Alladditions, deletions, and modifications to the invention, as disclosedherein, which fall within the meaning and scope of the claims are to beembraced thereby.

What is claimed:
 1. A method for supporting a substrate duringprogrammed material consolidation of one or more objects on or adjacentto the substrate, comprising: securing the substrate in position over asupport surface; and preventing unconsolidated material from contactinga bottom surface of the substrate.
 2. The method of claim 1, whereinsecuring the substrate in position over the support surface is effectedby positioning the substrate at least partially within a receptacleformed by at least one raised element.
 3. The method of claim 2, whereinsecuring the substrate in position over the support surface includesdisposing a retention lip extending laterally from the at least oneraised element over at least a portion of a periphery of the substrate.4. The method of claim 3, wherein the retention lip contacts at leastthe portion of the periphery of the substrate.
 5. The method of claim 4,further comprising: positioning at least one spacer between the supportsurface and the bottom surface of the substrate.
 6. The method of claim3, wherein disposing the retention lip comprises forming the retentionlip by programmed material consolidation processes.
 7. The method ofclaim 6, wherein forming the retention lip by programmed materialconsolidation processes includes employing stereolithography.
 8. Themethod of claim 3, wherein disposing the retention lip comprisespositioning a preformed retention lip over at least a portion of aperiphery of the substrate.
 9. The method of claim 2, whereinpositioning the substrate comprises positioning the substrate within areceptacle formed by at least one raised element that substantiallysurrounds the at least one substrate.
 10. The method of claim 9, furthercomprising: disposing at least one extension element on an upper surfaceof the at least one raised element.
 11. The method of claim 10, whereindisposing the at least one extension element comprises fabricating theat least one extension element by programmed material consolidationprocesses.
 12. The method of claim 11, wherein forming the at least oneextension element by programmed material consolidation processesincludes employing stereolithography.
 13. The method of claim 2, whereinsecuring the substrate in position over the support surface includesapplying a negative pressure to the bottom surface of the substrate. 14.The method of claim 13, wherein securing the substrate in position overthe support surface further includes positioning the substrate over asealing element with a peripheral portion of the bottom surface of thesubstrate contacting the sealing element.
 15. The method of claim 14,further comprising: breaking a seal between the sealing element and thebottom surface of the substrate.
 16. The method of claim 1, whereinsecuring the substrate in position over the support surface includesapplying a negative pressure to the bottom surface of the substrate. 17.The method of claim 1, further comprising: removing the substrate fromthe support surface.
 18. The method of claim 17, wherein removing thesubstrate comprises applying a positive pressure to the bottom surfaceof the substrate.
 19. The method of claim 18, wherein applying apositive pressure to the bottom surface of the substrate includescreating a circulating air flow beneath the bottom surface of thesubstrate.
 20. The method of claim 19, wherein creating a circulatingair flow beneath the bottom surface of the substrate causes thesubstrate to hover over the support surface.
 21. The method of claim 17,wherein removing the substrate comprises applying force to the bottomsurface of the substrate.
 22. A programmed material consolidationmethod, comprising: positioning at least one substrate in a receptacleof a retention system including a raised periphery that laterallysurrounds the at least one substrate; introducing unconsolidatedmaterial onto a surface of the at least one substrate; and programmablyconsolidating at least portions of the unconsolidated material.
 23. Theprogrammed material consolidation method of claim 22, whereinintroducing unconsolidated material comprises forming a layer ofunconsolidated material of desired thickness over the at least onesubstrate, then selectively consolidating regions of the layer.
 24. Theprogrammed material consolidation method of claim 23, whereinintroducing unconsolidated material further comprises repeating the actsof forming and selectively consolidating at least once.
 25. Theprogrammed material consolidation method of claim 22, whereinintroducing unconsolidated material includes substantially filling thereceptacle with unconsolidated material.
 26. The programmed materialconsolidation method of claim 25, further comprising: planarizing asurface of the unconsolidated material within the receptacle.
 27. Theprogrammed material consolidation method of claim 26, whereinplanarizing is effected with at least one of a meniscus blade and an airknife.
 28. The programmed material consolidation method of claim 22,wherein introducing unconsolidated material comprises sprayingunconsolidated material onto at least a portion of the at least onesubstrate.
 29. The programmed material consolidation method of claim 22,wherein introducing unconsolidated material comprises dispensing theunconsolidated material in a laminar flow.
 30. The programmed materialconsolidation method of claim 29, wherein dispensing is effected withoutintroducing unconsolidated material onto structures that protrude fromthe at least one substrate.
 31. The programmed material consolidationmethod of claim 22, further comprising: removing excess unconsolidatedmaterial from the recess following the progammably consolidating. 32.The programmed material consolidation method of claim 22, furthercomprising: preventing unconsolidated material from contacting a bottomsurface of the at least one substrate while introducing unconsolidatedmaterial into the receptacle.
 33. The programmed material consolidationmethod of claim 22, further comprising: removing the at least onesubstrate from the receptacle following programmably consolidating atleast portions of the unconsolidated material.